1. Field of the Invention
The present invention relates to a drive device for use in vehicles having rotating electrical machines that serve as a driving force source and a planetary gear unit.
2. Description of the Related Art
In recent years, hybrid vehicles, which are include an engine and rotating electrical machines, such as a generator and a motor, as a driving force source of a vehicle, have attracted attention in terms of fuel economy, environmental protection, and the like. Drive devices for hybrid vehicles generally require a control device for controlling the rotating electrical machines. Because the rotating electrical machines and the control device, which are operated in combination, are connected by connection members such as power cables, it is desirable, for convenience of installation in a vehicle, to integrate the rotating electrical machines and the control device in a unitary case. Accordingly, drive devices commonly use a structure in which an inverter case accommodating a control device is integrally provided on top of a drive device case accommodating two rotating electrical machines, a differential gear unit, and the like.
In such a structure of the drive devices, however, because the control device is provided on top of the drive device case, the overall vertical dimension of the drive device is increased. Thus, installing such a drive device on a vehicle requires the relocation of equipment such as a battery and an air cleaner, which are usually provided above the drive device, to other positions in order to prevent interference of such equipment with the control device.
In view of this problem, Japanese Patent Application Publication No. JP-A-2007-124764 (JP-A-2007-124764), for example, describes a drive device having the following structure. The drive device includes: an input shaft connected to an engine; two rotating electrical machines; a planetary gear unit having three rotating elements that are respectively connected to one of the rotating electrical machines, the input shaft, and an output rotating element; and a control device that controls the rotating electrical machines. Regarding the arrangement of the components included in this drive device, JP-A-2007-124764 describes a structure in which the two rotating electrical machines, the planetary gear unit, and the input shaft are provided coaxially, and the control device is provided above the drive device. The control device is provided radially outside one of the rotating electrical machines. Thus, a condenser and a reactor, which are relatively large components among the components of the control device, are provided opposite each other with respect to a vertical plane extending through the rotation axis of the rotating electrical machine, whereby these relatively large components can be efficiently accommodated in a drive device case. This structure thus suppresses increases in the height of the drive device.
In the drive device as described in JP-A-2007-124764, however, two rotating electrical machines are provided coaxially. Thus, the axial length of the rotating electrical machines need to be increased in order to increase the rotational driving force that can be output from the rotating electrical machines, while suppressing the dimensional increase in height of the drive device. This increases the axial length of the drive device. That is, in conventional drive devices, integrating the control device necessarily increases either the overall height or the axial length of the drive device, thus increasing the overall size of the drive device.